Twin-tunnel kiln



Feb. 7, 1928. I 1,658,332

W. L. HANLEY, JR I TWIN TUNNEL KILN Original Filed Oct. 8, 1925 2 Sheets-Sheet 1 VIIIIII'IIIII III:

IIIIIIIIIIIIIII Recuper nfor ecu emf Feb. 7, 1928.

' W. L. HANLEY, JR

TWIN TUNNEL-KILN Original Filed act. a, 1925 2 She ets-Sheet 2 Patented Feb. 7, 1928 UNITED STAT WILLIAM LEE HANLEY, an, or imanronn, rnmzsrnvanm."

rwm-runnnn KILN.

Applicationfiled October 8, 1925,:Seria1 No, 61,360. Renewed July 19, 1927.

plicable to kilns for firing other classes of moving in opposite directions, in such The ObJect ofmy invention is to prov de I a tw1n tunnel kiln having goods-conveying means extending on two-parallel tracks and a manner as to provide a simple and compara tively inexpensive structure which can be.

preeheating and cooling chamber of the kiln cheaply built and kept in repair'and workable condition at slight expense, and which will be highly etHcientinfiring thebrickand also in handling an extremely large. quantity and giving a very high output. In carrying my invention into effect, I con-, struct a. twin tunnel kiln as a duplex .structure throughout its entire length, that is to .say, comprising two sidewalls and a 'centrally-and longitudinally located impervious wall or partitionextending throughout the. entire length of the kiln and producing two parallel tunnels separated by. the said central wall at all points. The central portion of the kiln forms a duplex'firing chamberx independently controlling them so as to regwhich is accomplished bv'means of the inprovided with two filing zones, e'ach'heated by an independent series of furnaces. arranged along the outer side" ofjthe. firing zone, and discharging their products 'of combustion over a bafile wall into the firing zone directly uponthejgoods to be fired, the, said furnaces being provided with means for 1 ulate' the temperature of different portions of each firing zoneand-tograduallyincrease the temperature from the. entering end of. the firingzon'e to the discharging end there of, in accordance with apre-determined rising heat curve, it'. being understood that the heat curve in one firing zone will be the opposite of that in the other firing zone,

' dependent regualtion. of the furnaces and the complete separation of the two zones by the central impervious wall. The/endportions of the kiln at each end ofthe firing 'l chamber constituteduplex pro-heating. space, eaehpf said pipes or-p is.

products'of combustion fromeach of the thereof and preferablylocatedat the base coolingchambers, each comprising through lout itslengtlrtwo separatedtunnels, in one of which cars of fired brick leaving the firing zone in alignment therewith, are moving toward the end ofthe kiln and giving up the heat of said fired-brick gradually andprogressively-to the central partition wall are being gradually preheated,. watersmoked and oxidized. The central partition wall is preferably made thinner, through the I preheating and cooling zones, than through the firing: chamber, to facilitate radiation, I

As the two tunnel sections of each duplex the pre-heat'ing tunnel on the other side thereof, and 1 construct the duplex pre-' heating. and cooling chambers of the kiln of such length that the products in the preheatingzone of-eachof these duplex end sections will be raised to ap roximately the temperature at the inlet entllof the aligned firing zones of the duplex firing chamber in traversing he distance from the end of thekiln to the firing zones. It. is of the utmost importance that the ring zones be kept out of the corresponding'or aligned .pre-heatin g zones, for the reason that the presence of such products of combustion .in the preheating zone interferes with the properjoxidation of the clay products, as they contain no-free oxygen and they also produce scumming orstaining during the water smoking of the brick. I there- .fore provide each firing zone of the duplex firing chamber with means for withdrawing therefromall of the products of combustion discharged into the firingzone by its furnaces, and I preferably provide .a' pipe or passage adjacent to each of said'furnaces, for withdrawing the products of combustion of a. deflecting wall, betweenthe inlet passages from-the furnaces, and the adjacent goods space, .over the top of whichb'ridge wall the products of combustion enter said m and the other at A constructed as a duplexstructure comprisbeing provided witha regulating valve or damper so that the regulation of these discharge pipes assists in the regulation of the heat in the difi'erent portions of each firing zone and the maintenance of the desired curve. by means of these dampers, 1 may also withdraw not only the products of combustion, but some of the air from the aligned end portions of the kiln, causing them to be replaced by fresh air and insuring that the pro-heating shall proceed in the presence of fresh air containing the required amount of oxygen. The products of combustion withdrawn from the several furnaces of each firing zone are preferably conducted through a recuperator and caused to heat quantities of fresh air which is conducted to the driers in which the clay products are dried preparatory to firing or burning, thus conserving the heat of the products [of combustion, while eliminating them from the respective firing zones,

Referring to the accompanying drawings, which illustrate diagrammatically a kiln embodying my presentinvention,

Fig. 1 represents a diagrammatic top plan View of my improved twin tunnel kiln.

Fig. 2 represents a horizontal section of the kiln drawn to a larger scale, parts being broken away.-

Fig. 3 represents a vertical transverse section, drawn to a larger scale through the duplex firing chamber. 7

Fig. et is a similar sectional view taken 5 through one of the duplex pre-heating and cooling end sections of the kiln.

Referring to the kiln illustrated in the accompanying drawings, A, represents the duplex firing chamber of my improved kiln. whichis located centrally with respect to the length of the kiln and is provided at each end with a duplex cooling and pre-heating chamber, one of which is indicated at A The entire tunnel is ing lateral walls, 1, 1, a central impervious partition wall, 22 2. 2, and separate crowns or roofs, 3, 8, of any usual or preferred construction, forming two tunnels 4:. 4, throughout the entire length of the kiln. Each tunnel is provided with a track. the rails of which' are indicated at 16, 16. for a line of tunnel cars, 17, diagrammatically illustrated in Fig. 3 and Fig. 4, extending the entire length of the kiln on each set of tracks, said cars being moved in the respective tunnels in opposite directions, as indicated bythe arrows in Fig. 2. Each tunnel will therefore comprise a pre-heating zone within one of the end sections of the kiln,

' ac'entral firing zone within the duplex firing chamber, A, and a cooling zone within the other end section of the tunnel kiln, the

arrangement of these respective zones being the reverse in one tunnel of the arrangement in the other. The central partition is preferably made thinner where it extends between the cooling and pre-heating zones at each end of the kiln, as indicated at 2*, 2, to facilitate radiation, and these portions are termed radiating portions of the partition, while the centralportion, 2, interposed between the firing zones, is termed the substantially non-radiating portion. 7

A Fig. 3 represents a transverse sectional View through the firing chamber, showing the two firing 'zonesand the heating furnaces therefor. At the outer side of the tunnel of each firing zone, is located a plurality of furnaces, 5, for the combustion of any desired character of ,fuel, gas, oil, wood, coal, etc, which may be supplied in any appropriate manner, and provided in any usual manner with the necessary air to insure the proper combustion of the fuel. In the present instance I have shown a heating nozzle indicated at 5, and supplied with air and gas from an air pipe, 5", and gas pipe, 5, underthe control of suitable regulating valves, indicated respectively at 5 and 5, so that the combustion in each furnace can be regulated to efiect the regulation of the temperature in the corresponding portions of the adjacent firing zones. 'The furnaces are located on opposite sides of the firing chamber. exterior to the adjacent firing zones. Within each of the firing zones I locate a vertical deflecting wall, or baflle wall, indicated at 9,. between the furnace and adjacent goods space, the said wall extending upwardly from the back walls of the furnaces and tapering toward thegtop, the upper portion being preferably curved or inclined inwardly toward the goods space, as indicated at 10. Each of the deflecting walls, 9, is provided on its inner face at approximately the level of the upper face of the tunnel cars, 'with an eduction port, 11. adjacent to each of the furnaces, or in other words located between adjacent furnaces, said eduction ports each forming part of an eduction passage indicated at 12. extending to the outside of the. firing chamber and communicating with an eduction pipe or header, 'le't so that the products of combustion of each furnace may be with-- drawn from the firing zone after they have imparted their highest heat to the goods on the cars within the adjacent firing Zone. The inner face ofeach of the baflle walls is provided with one or more longitudinal ribs, indicated at 22, at different elevations above the trucks or cars. for the purpose.

of preventing the products of combustion 13, and will be discharged downwardly, from the roof or crown of each firing zone, upon,"

through and around the goods, descending to the lower portion of the goods space and passing-out through the eduction ports and passages to the eduction pipe or header, 14 The battle walls, 9, and the central wall, 2, are provided respectively with projecting flanges, 21 and 20, as usual, extending above the lateral portions of the tunnel cars to protect. the cars from the injurious effects of the high temperature within the firing zones, and these flanges are continued also through the duplex end sections of the kiln, as indicated in Fig. 4:. The eduction passages are thus located below the portions of ,the deflecting wall which lie between the inlet passage, 13, for the products of combustion and the adjacent goods space, into which said passage, 13, discharges over the top of said deflecting wall. The eduction pipes, 14, are each shown connected to a recuperator, 30, so that-they pass through the same for the purpose of heating air which is passing through the recuperator out of immediate contact with the products of combustion. In this in stance, I have shown the recuperator as consisting of a receptacle containing a heating coil connected with the adjacent pipe, 14, and-to-a suction fan, 32, soa's to withdraw the products of combustion from the adjacent furnaces and pass them' through the recuperator which is supplied with fresh air through a pipe indicated at The air from the recuperator. is heated and is delivered into the adjacent air pipe, 5*, for supplying airto thefurnaces for combustion. The products of combustion,.after giving up a very considerable portion of their heat, are preferably-carried to a drier, 34, and passed through heating coils, 35, or passages therein, for heatingthe air within the drier and by radiation and convection utilizing the heatof the spent gases in dry ing the products before they are taken to the kiln to be -fired.- From the drier heat coils or passages, 35, the products of combustion pass to a stack, 36. Some of the air heated by the 'rec'uperator may also be .taken .to the drier and admitted thereto directly in contact with the brick by means of a pipe, 37, for example, under the con trol of a suitable valve, 38, if desired, and the air supplied to the recuperator will be furnished by a fan or blower, indicated at 40. i 4

In some instances the air, or portions of the air, heated by the products of combustion, may be conducted from the recuperator. to one or both of the preheating zones to aid in preheating the product. InFig. 1, for example, I have shown the recuperators, 30, each connected by a'pipe, 50, provided with a valve or damper, 5 1, to a head er, 52, connected by branch pipes, 53, with the adjacent preheating zone, each branch preferred construction, although it is 10b vious that a single recuperator could be made of sufiicient size to handle the products of 'combustion from both sets of furnaces and supply heated air to both sets of burners and to the desired number of driers by making the necessary pipe connections.

In the operation of my improved kiln, I prefer to so regulate the furnaces of each tiring zone that the temperature adjacent to the entering end thereof will be approximately froiii900 F. to 1400" F. In the drawing, Fig. 2, I have noted, for example, the temperature at 1100 F. at the entering end of' each firing zone. The temperature within each firing zone will be gradually increased according to a predetermined heat curve by regulating the several furnaces to a temperature of approximately 1800 F. to 2100 F. at the discharge end of the firing zone. In Fig, 2 I have indicated at the discharge end of each firing zone, by. way of example, a ten'iperature of 2000 F. It will" thus be seen that'the highest temperature in 'one firing zone is opposite the lowest tem ber, A, and by the regulation of the fur-- naces ofeach firing zone, by means of the valve controlling the admission of air and fuel and the withdrawal of the products of combustion, the desired heat curve in each hit) firing zone can be maintained very -acculately. i i

It will also be noted that the separate tunnels, l, at, of each of the end sections, A and- A are separated from each'otherthroughout their len th by the central impervious ature at the entering end of the adjacent 1 firing zone. by the time it reaches the firing zone. It will be understood that each set of tracks, 16, carries a line of cars extending throughout the entire length of the tunnel, the said carsbeing moved in opposite directions in the separate tunnels, either continuously or intermittently, a car of green brick being inserted in the pro-heating zone of each t nel; 4, as a car of fired and' cooled brick is'removed from said tunnel at the opposite end thereof. The trains of tunnel cars may be advanced in any usual or desired manner.

In constructingmy improved tunnel kiln the duplex end portions can be constructed of an ordinary brick and will be of very cheap and at the same time durable construction. The firing chamber. will involve the use of a considerable quantity of refractory material, as fire 'brick, but as there are no longitudinal fines within the walls or roof,

the construction is comparatively inexpensive and the construction of the entire kiln is so simple that it is a comparatively easy matter to keep the kiln in repair at all times, and it may be used for-very extensive periods without any repairs. This is an important item, as twin tunnel kilns are necessarily very expensive in their initial cost and in orderto operate them economically, 1t is necessary to obtain not only a'large,

but a continuous, output. Itwill also be noted that great economy in fuel is obtained the preheating, water-smoking and oxida in my improved kiln, in addition to securing the other-technical effects desired. By the discharge of the products of combustion into the firing chamber, the highest efliciency in the firing-operation can be obtained and by withdrawing the products of combustion,

tion of the products will be. performed in clean air. free from products of combustion.

the drier or driers, so that comparatively By my construction the air is heated toa ofa duplex firing chamber having two firlittle of the heat of the products of combustion is wasted, and the kiln can thus be operated continuously and at high efficiency.

It is also to be noted that I-withdraw the hot products of combustion from the firing zone and conduct them directly to the recu-' perator, so that the air passed through the,

recuperator is heated to a much higher temperature than is possible where the gasesare conducted through muffles or heating.

passages where they give up the larger portion of their heat and are then conducted to recuperating means to utilize the comparatively low temperature residual heat which may remain in them. The air in such cases is not raised to a suflicie'ntly high temperature for efiicient preheating, or for securing the highest eificiency of the burnersl temperature very nearly as high as that'existing in the firing zone itself, andthis highly heated air may be employed efficiently for preheating purposes, .for example, and will also be highly eificient in pro moting combustion in the furnaces.

\Vhat I claim and desire to secure by Letters Patent is: d v. y d

1. In a twin tunnel kiln, the combination of a duplex firing chamber, having two firing zones separated by a vertical longitudi nal impervious wall and provided with rows .of furnaces located on oppositesides of the duplex firing chamber, the furnaces of each row communicating directly with the adjacent firing zone, means forwi thdrawm the products of combustion from eachfiring zone. a duplex tunnel section extending longitudinally from each end of the duplex firing chamber, each comprisinga pre-heating chamber communicating with the inlet end of one firing zone and a cooling chamber communicating with the discharge end of the other firing zone, said preheating and cooling'chambers .being separated by an impervious wall forming a continuation of the: longitudinal "wall between the firing zones, andparallel goods conveying means movable. in opposite directions, each of which passes through one of said firing zones and the pro-heating and cooling chamhers at the opposite ends thereof.

2. In a twin tunnel kiln, the combination of a duplex firing chamber, having two firing zones separated by a vertical longitudinal impervious wall and provided with rows of furnaces located on opposite sides of the duplex firing chamber, the furnaces of each row communicating directly with the adjacent firing zone, means for withdrawing the products of combustion from each firing zone, a duplex tunnel section extending longitudinally from each end of theduplex firing chamber, each comprising a pre-heating chamber communicating with the inlet end of one firing zone and a cooling. chamber communicating with the discharge end of the other firing zone, said preheating and cooling chambers being separated by an impervious wallforming a contin uation of the longitudinal wallbetween the firing zones, and parallel goods conveying means movable in opposite directions, each of which passes through one of said ,firing zones and the pre-heating and cooling chambers at the opposite ends thereof, each of said furnaces being provided with heat regulating means whereby the furnaces for one of the firing zones. can be regulated to provide a rising heatc'urve'inone direction longitudinally thereof,-and the furnaces for the other firing zone can be regulated to provide a rising heat curve extending longitudinally thereof, in the opposite direction. 3. In a twin tunnel kiln, the' combination ing'zones separated by a vertical longitudinal impervious wall, and provided with rows of furnaces located on opposite sides of the duplex firing chamber, the furnaces of each row communicating directly -with the adjacent firing zone, means for independently regulating each of said furnaces to control the heat thereof, an eduction pas:

sage adjacent to each of said furnaces of each row, for withdrawing the products of combustion from the interior of the adjacent firing zone, independent regulating means for each of said eduction passages, a duplex section extending longitudinally from each end of the duplex firing chamber, and each comprising a pre-heating chamber communicating withthe inlet end of one firing zone, and a cooling chamber communicating with the outlet end of the row communicating directly with the adja- -cent firing zone, a duplex tunnel section extending longitudinally from each end of the duplex firing chamber, each comprising a pie-heating chamber communicating with the inlet end of one firing zone, and a cool-n ing chamber communicating with the discharge end of the other firing zone, said pro-heating and cooling chambers being separated by an impervious wall forming a con-,

' tinuation of the longitudinal wall between the firing zones, and parallel, goods conveying means movable in opposite directions, each of which passes through one of said firing zones and the pre-heating and cooling chambers at the opposite endsthereof, re-

cuperating means provided with air pas;-

sages. for heating air, air connections from .said recuperating means to a point of use,

and means for withdrawing the products from each firing zone and conducting them directly tosaid recuperating means. M

tunnel kiln, the combination a of a duplex firing chamber, having two firin 'zones separated by a vertical longitudina 5. In a twin impervious wall and provided with'rows of furnaces located on opposite sides of the duplex firing chamber, the furnaces of each row communicating directly with the adjacent firin zone, a-duplex tunnel section extending longltudinally from each endof the duplex firing chamber, each comprising a preheat ing chamber communicating 'with the inlet end of one firlng zone and a cooling. chamber communicating with the discharge endof the other firing zone, said pro-heating and cooling chambers being separated by an im pervious wall forming a continuation of the longitudinal wall between the firing zones, and parallel goods conveying means movable in opposite directions, each of which passes through one of said firing zones and the pro-heating and cooling chambers at the opposite ends thereof, recuperating means air, air connections from said recuperating means to a point of-nse, and means located ad acentto each furnace for Withdrawing the provided-with air passages for heating fresh products of combustion from the firing zone adjacent thereto, and conducting them directly to said recuperative means. 6. In a twin tunnel kiln, the'combination of a duplex firing chamber, having two firing zones separated by a vertical longitudinal impervious wall and provided with rows of furnaces locatedon opposite sides of the duplex firing chamber, the furnaces of each row communicating directly with the adjacent firing zone, a duplex tunnel section extending longitudinally from each end of the duplex firing chamber, each comprising a pie-heating chamber communicating with the inlet end of one firing zone, and a cooling chamber communicating with the discharge endof the other firing zone, said preheating and cooling chambers being separated by an impervious wall forming a continuation of the longitudinal Wall between the firing zones, and parallel goods conveying means movable in opposite directions, each of which passes through oneof said firing zones and the pro-heating and cooling chambers at the opposite ends thereof, recuperating means provided with air passages for heating air, air connections from said recuperating means to each preheating chamber, andmeans for withdrawing the products of combustion from. each firing zone lUO and conducting them directly to the recuperating means. I a v '7. In a twintunnel k ln, the combination of' a duplex firing chamber, having two firing zones separated by a vertical longitudinal impervious wall and provided with rows of furnaces located on opposite sides of the duplex firing chamber, the-furnaces of each row communicating directly with the adjacent firing zone, aduplex tunnel section extending longitudinally from-each end of the duplex firing chamber; each comprising a .pre-heating, chamber communicating with the inlet end of one firing zo-ne, and a cooling chamber communicating with the discharge end of the-other firing zone, said pro-heating "and cooling chambers being separated by an impervious wall forming a continuation of the' longitudinal wall between the firing,

zones, and parallel oods conveying means movable in opposite irections, each of which passes through one of said firingzones and the pre-heat-ing and cooling chambers atthe oppos te ends thereof, recuperating means provided with air passages for heating air,

air connections from the said recuperating means to each preheatin chamber, coinmunicating therewith at di 'erent points longitudinally thereof, means for independently controlling the admission of air heated by therecuperating means at said different points, and means for withdrawing the products. of combustion from each firing zone and delivering them directly to said recuperating means.

8. In a twin tunnel kiln the combination of a duplex firing chamber, having two firing zones separated by a vertical longitudinal impervious wall and provided with rows of furnaces located on opposite sides discharge end of the other firing zone, saidv pre-heating and cooling chambers being separated by an impervious wall forming a continuation ofthe longitudinal wall between i tending longitudinally from each end of the the firing zones, and parallel goods conveylng means movable in opposite directions, each of which passes through one of said firing zones and the pre-heating and cooling 7 chambers at the opposite ends thereof, recuperating means provided with air passages for heating air, air connections from said recuperating means to each preheating chamber including branchpipes discharging into said chambers at different points longitudinally thereof, independent controlling means for said branch pipes, and means for withdrawing the products of combustion from each firing zone-located ad jacent to each of said furnaces and for conducting said products of combustion directly'to said recuperating means.

9., In a twin tunnel kiln, the combination of a duplex firing chamber, having two firing zones separated by a vertically, longitudinal, impervious wall, and provided with rows 'of furnaces located on. opposite sides of the duplex firing chamber, the furnaces of each row communicating directly with the adjacent firing zone, a baflie wall interposed between each row of furnaces and the adjacent firing zone, means for withdrawing the products of combustion from each firing zone, a duplex tunnel section vexduplex firing chamber, each comprising a preheating chamber communicating with the inlet end of one firing zone, and a cooling chamber communicating with the discharge end of the other firing zone, said preheating and cooling chambers being separated by an imperviops wall in alignment with and forming a continuation of the longitudinal wall between firing zones, and parallel goods conveying means movable in opposite directions, each of which passes through one of said firing zones and the preheating and cooling chambers at the opposite ends thereofr 10. In a twin tunnel kiln, the combination of a duplex firing chamber having two firing zones arranged side by side and separated by a vertical, longitudinal, impervious, and substantially non-radiating wall,

two rows of furnaces located on opposite a communication with the discharge end of the other. firing zone, said preheating and cooling chambers at each end of the kiln being separated by an impervious radiating wall of less thickness than the wall between the firing zones and parallel goods conveying Zfiring zones separated by a vertical, longitudinal, impervious wall, and provided with rows of furnaces located'onoppositesidcs ofthe duplex firing chamber, the furnaces of each row communicating directly with the adjacent firing zone, a. bafile wall interposed between each row of furnaces and the adjacent firing zone, and providing an inlet passage on one side of said b'afile wall and over the top, for the products of combustion, from the row of furnaces to the adjacent firing zone, a dupIex'tunnel section extending longitudinally from each end of the duplex firing chamber, each comprising a preheating. chamber communicating with the inlet end of one firing zone, and a cooling chamber communicating with the discharge end of the other firing zone, said preheating and cooling chambers being separau ed by an impervious wallinalignment with and forming a continuation of the longitudinal' wall between firing zones, and parallel goods conveying means movable in opposite 'dlrections, each of which passes through one of said firing zones and-the preheating and coohng chambers at the opposite ends thereof, recuperating means provided with air Hit) passages, and eduction passages extending from each firing zone, transversely to the exterior of the kiln, below the portions of' the baffle wall lying. between each firing zone and the inlet passage from the adjacent furrows of furnaces located on opposite sides of the duplex firingchamber, the furnaces of each row communicating directly with the adjacent firing zone, a bafiie wall interposed between each row of furnaces and the adjacent firing zone, and providing an inlet pas sage on one side of said bafile wall and over the top, for the products of combustion from the row of furnaces to the adjacent firing zone, a duplex tunnel section extending'longitudinally from each end of the duplex tiring chamber, each comprising a preheating chamber communicating with the inlet end of the firing zone, and a cooling cham ber communicating with the discharge end of the other firing zone, said preheating and cooling chambers being separated by an impervious wall in alignment with and forming a continuation of the longitudinal wall between firing zones, and parallel goods conveying means movable in opposite directions, each of which passes through one of said firing zones and the preheating and cooling chambers at the opposite ends thereof, recuperating means provided with air passages, eduction passages extending from each firing zone,'transversely to the exterior of the" kiln,-blow the portions of the bafile 'wall lying'between eachfiring zone and the inlet passage from, the adjacent furnaces,

said eduction passages being directly connected to the recuperating means, means for conductingheated air from the recuperating means to the preheating chambers and distributing it thereto at different points longitudinally thereof, and independently controlled dampers for independently regulating the admission of heated air "to the preheating chambers points.

13. In a twin tunnel kiln, the 'coinbination with a firing chamber provided with furnaces communicating therewith, of a duplex tunnel section extending longitudinally from each endof the firing chamber, each comprising a preheating chamber anda cooling chamber communicating with the firing chamber, said preheatingand cooling ehambers being separated by an impervious wall, parallel goods conveying means movable in opposite directions,- each of which passes through the firing chamber and the preheating and cooling chambers at the opposite ends thereof, recuperating means pro-".

at such different vided with air passages for heating air, air

connections from said recuperating means to a. point of use, and means for withdrawing the products of combustion from the firing chamber and conducting them to said recuperating means,

1 L Ina twin tunnel kiln, the combination with a firingchamber provided with furnaces conmiunicating therewith, of a duplex tunnel section extending longitudinally from each end of the firing chamber, each comprising a preheating chamber and a cooling chamber communicating with the firing chamber, said preheating and cooling chambers being separated an impervious wall,

parallel goods conveying means movable in opposite directions, each of which passes through the firing chamber and the pre' heating and cooling chambers at the opposite ends thereof, recuperating means provided with air passages for heating air, air connections from said recuperating means to a point of use, and means located adjacent to each furnace for withdrawing the products of combustion from the firing chamber adjacent thereto and conducting them to said recuperator. I l

'15. In a twin tunnel kiln, the combination with a firing chamber provided with furnaces communicating therewith, of a duplex tunnel section extending longitudinally from each end of the firing chamber, each comprising a preheating chamber and a cooling chamber communicating with the firing chamber, said preheating and cooling chambers being separated by an impervious wall, parallel goods conveying means movable in opposite directions, each of which passes through the firing chamber and the preheating and cooling chambers at the opposite ends thereof, recuperating means provided with air passages for heating air, air conlit) loo

neetions from said recuperating means to wall, parallel goo s conveying means mov able in opposite directions, each of which passes through. the firing chamber and the vprehe atin-g and cooling chambers at the opposite ends thereof, recuperating means pro" vided with air passages ion heating air, air connections from said recuperating means to each preheating chamber communicating therewith atdifierent points longitudinally f jacent row of furnaces, a duplex tunnel sec- .and providing an inlet passage on one side of said baffle wall and over the top thereof for the products of combustion from the adtion extending longitudinally from'each end of the firing chamber, each comprising a preheating chamber and a cooling chamber, said preheating and cooling-chambers being separated by an impervious wall, and parallel goods conveying means movable in opposite directions, each of which passes through the firing chamber and the preheating and cooling chambers. at theopposite ends thereof, of recuperating means provided with air pass-es, and eduction passages extending from the firing chamber transversely to the exterior of the kiln below the portions of the bafile walls lying betweenthe adjacent goods space and the in- .let passage from the adjacent furnaces, said eduction passages being connectedto the recuperating means. 18. In a twin tunnel kiln, the combination with a firing chamber provided with rows offurnaces located on opposite sides there-' of and-communicating directly with the interior of the firing chamber adjacent thereto,-a baffle wall interposed between each rowof furnaces and the adjacent firing zone,

and providing an inlet passage on one side of said baffle wall and over the top thereof for the products of combustion from the adjacent row; of furnaces, a duplex tunnel section extending longitudinally from each end of" the firing chamber, each comprising a preheating chamber and a cooling cham-' her, said preheating and cooling chambers being separated by an impervious wall, and parallel goods conveying means movable in opposite directions, each of which passes through the firing chamber and the preheating and cooling chambers at the opposite ends thereof, of recuperating means provided with air passages, and eduction passages extending from the firing chamber transversely to the exterior of the kiln below the portions of the baffle walls lying between the adjacent goods space and the lnlet passage from the adjacent furnaces, said eduction passages being connected to the recuperating means, means for conducting heated air from the recuperating means to the pre heating chambers and distributing it thereto at different points longitudinally thereof,

and independently controlled means for independently regulating the admission of heated air to the preheating chambersat such different points.

In testimony whereof I ,affix my signature.

WILLIAM L; HANLEY, J5. 

